The present invention pertains to engine management systems such as those found on automobiles and more particularly to an engine management system that is capable of meeting super ultra low emissions vehicle requirements for evaporative emissions.
Automobile manufacturers have gone to significant lengths to reduce emissions created by vehicles. Most automobiles contain many differing sources of emissions of various types. Manufacturers have pursued a number or these sources in an ad hoc manner. Two major classes of sources of emissions are the exhaust emissions, and evaporative emissions from other sites on the vehicle. Both classes of emissions include hydrocarbons or unburned fuel. The major source of unburned fuel is obviously the gasoline to be burned by the engine. In today""s vehicles, fuel tanks are vented through carbon canisters so that hydrocarbons are removed form the gases vented from the fuel tank due to a pressure differential. The vapors from the fuel tank are stored in the carbon canister until the evaporative emission hydrocarbons can be pulled into the engine and burned in the combustion process.
The system described above is very effective at stopping fuel vapors escaping from the fuel tank. However there are no systems in place that address fuel permeating from other sites such as: the regulator diaphragm and regulator to rail interface seal; the seals at the rail/injector interface (all fuel rail seals that seal high pressure fuel including fuel rail cross-over pies and end plugs); the seals at the inlet and outlet to the rail; vapor losses form the crank case through the PCV system into the induction system; and vapor losses from dripping injectors, reversion, wall wetting or other sources of hydrocarbons that escape to the atmosphere from the intake manifold through the induction system, the EGR system (if present) and exhaust systems.
Further, it is known that hydrocarbon emissions loss can also result from fuel vapor molecules that permeate past plastic and elastomeric materials. In current fuel systems this includes xe2x80x9c0xe2x80x9d ring type seals, rubber or plastic fuel lines, plastic fuel rails and injectors, plastic fuel tanks, and the rubber fuel pressure regulator diaphragm. FIG. 1 shows the previously mentioned known components and system with arrows pointing outward to represent the fuel permeation losses.
A second type of emissions loss is migration losses. After the engine is shut off, some unburned fuel vapors exist in the engine""s intake manifold and cylinder head. These vapors can migrate form the intake manifold past the throttle body and air cleaner to reach the atmosphere. Likewise, some hydrocarbon emissions from fuel may exist in the engine oil. Again, vapors from the engine oil in the crankcase can migrate through the PCV fresh air supply through the air cleaner reaching the atmosphere. Also, it is common and known that unburned hydrocarbons typically exist in the engine""s exhaust system. These vapors may migrate through the exhaust system to reach the atmosphere.
A third source of emissions of hydrocarbon are fuel leaks at system component interfaces. The diagram shows the large number of interfaces that exist in a current system.
The above are generally small contributors to the total evaporative emission picture when looked at individually. However, in order to meet aggregate emission requirements, fuel system, engine suppliers, and vehicle manufacturers will have to reduce the number of permeation sites that can emit hydrocarbons. In other words the collective emissions of all these xe2x80x9cuncontrolledxe2x80x9d sites will have to be addressed.
Rather than optimizing each permeation site through extensive development, resulting in less service friendly metal connections or eliminating permeation sites, the present invention proposes another approach to contain the emissions escaping from these sites and use them as part of the normal combustion process.
The present invention relates to a manifold, fuel system and induction system architecture that contains fuel vapors that normally occur inside the intake manifold and prevents them from migrating to the atmosphere. The containment of hydrocarbons according to the present invention is achieved by the use of one or more shut-off devices in combination with strategically minimizes permeation sites by moving them inside the intake manifold where the aforementioned shut-off devices can also contain evaporative emissions form these sites.